[JuniorMint335]

2007 335i Stock motor @ 100k.

I am hearing this knocking sound from cylinders 1,2,4. The car came back a week ago from a head gasket job. In doing so they also replaced all the exhaust valves including a couple lifters because the mechanic accidentally damaged 2 valves. I didn't notice anything unusual until this afternoon when I opened the hood and heard this sound coming from the top of the engine. Now the sound is clear enough that i can hear it even with the hood is closed.

After I came home, I took the engine cover off and felt each coil pack and immediately noticed cylinders 1,2,4 were more shaky than the others. It feels like something is hitting it. I took the sparkplugs off and examine each one, they are looked fine. I then tighten it back and started the engine again, the sound persisted. Next I swapped the coils from the good cylinders to 1,2,4, only to find out the same result. Then I noticed when I press onto the latch of the coil on cylinders 1,2,4 the sound goes away. I can't make sense of this.

When I finally decide to call it a day and put everything back together, miraculously the sound fainted, but I can still hear a little bit. What the heck is going on??? Lifter knock??

Link below for the actual sound before I started my diagnostics.

Thanks in advance.

[Velocity26]

That sounds like a classic "rod knock" to me, but you would not be able to touch anything and make that go away.

They obviously pulled the head, and likely pulled the injectors out too. The injector seals must be replaced whenever an injector is pulled, even if it is put back into the same cylinder. It is possible that you are hearing some pressure blow past the injector seals. You might push on the fuel injectors, while you hear the noise, and see if that does anything.

Good luck

[bigdnno98]

a cylinder misfire can also sound like rod knock. Are you throwing any codes or have a half engine light or CEL?

[bigdnno98]

now that I've heard the video that doesn't sound like a cylinder misfire. does kind of sound like rod knock but I wouldn't just to the worst case scenario just yet. do like stated above and push down on the injectors to see if it affects the sound. Lots of different things can cause knocking sounds like that.

[Jeff@TopGearSolutions]

I'd bring it back to the mechanic and let them figure it out. They are the ones who messed with the engine afterall.

[JuniorMint335]

Originally Posted by bigdnno98

a cylinder misfire can also sound like rod knock. Are you throwing any codes or have a half engine light or CEL?

No codes present at the moment. There was a misfire on cylinder 4 before I got the car back. Thats when they found out 2 valves were damaged so they replaced the entire set of exhaust valves, seals, and lifters. That seem to have taken care of the misfire on cylinder 4.

Is there anything on the valvetrain that is sensitive to the touch like this? The valve cover is pretty sturdy and cant possible transfer any load onto the lifters guides and such.. So it must be something connecting to the coil cylinder?

[Velocity26]

Originally Posted by Jeff@TopGearSolutions

I'd bring it back to the mechanic and let them figure it out. They are the ones who messed with the engine afterall.

+1

[JuniorMint335]

Originally Posted by Velocity26

That sounds like a classic "rod knock" to me, but you would not be able to touch anything and make that go away.

They obviously pulled the head, and likely pulled the injectors out too. The injector seals must be replaced whenever an injector is pulled, even if it is put back into the same cylinder. It is possible that you are hearing some pressure blow past the injector seals. You might push on the fuel injectors, while you hear the noise, and see if that does anything.

Good luck

It could be pressure related because I feel the knock when I place my fingers over the coil. I'll try your recommendation and get back to you.

[JuniorMint335]

Originally Posted by bigdnno98

now that I've heard the video that doesn't sound like a cylinder misfire. does kind of sound like rod knock but I wouldn't just to the worst case scenario just yet. do like stated above and push down on the injectors to see if it affects the sound. Lots of different things can cause knocking sounds like that.

I had my rod bearings replaced last sept. The rod knock sounds a bit different and much higher pitch. I havent heard anything like that since the job. This new knocking sound is a result of replacing the HG. So last night after I put everything back including the engine cover, the sound really dampened down. I started the car this morning and the volume stayed the same. I tried to re-bleed the lifters, I did about 5-6 reps of holding my rpm at 2.5-3k for 20-30 seconds, then let it idle. Seem to quiet down just a little bit, but it could be psychological. Even new lifters shouldn't make such a pronounce sound... I hope they didn't mess up my valvetrain.

[JuniorMint335]

I apologize for the long summary.

Quick update** I touched everywhere including the injectors and other metal parts and the only thing that stops the sound are the coils. I took all the coils out of the knocking cylinders and inspected each barrel. They all seem normal so just out of curiosity I used a flat head screwdriver and push the tin shell inside the barrel further down thinking maybe its preventing the coils from not seating low enough. Sure enough most of the knocking noise went away, but it would knock at random cylinders 1,2,3,4 one at a time. WTFF! I tried to tighten them more with my hand by wiggling the coils left and right until the sound goes away. Now the knock seems to have disappeared in all cylinders except cylinder 3. While the car is running, i unplugged 3, but that resulted in making cylinder 4 knock. I quickly plugged it back and cylinder 4 was normal again and only 3 was knocking. Then I noticed out of all the coils cylinder 3 had a "ELDOR" brand coil while the rest are "BOSCH". The shop might have mixed it up with another 335 at the shop.

My question is, can a diff brand of coil really cause all this?? My spark splugs are also Bosch and they are fairly new. Less than 10k miles on it.

This video was taken before 3 became the problem.

[NapsterAU]

Any way you can check if gas is escaping around the plugs or possibly VCG?

Definitely doesn't sounds like rod knock or lifters from what I hear in the video.

[jtswole]

Question. Why did you replace the rod bearings? If it's because of a spun bearing, you can't just replace the bearing and away you go. You need to replace the rod that spun the bearing, as well. The rod bearing will fail again and that is what you might hear.

[Boland01]

My son's car spun a rod bearing on his 328i and you could hear the rod knock from inside the house. We drained the oil and looked at the filter and sure enough there was a bunch of metal. Then pulling the pan confirmed it.

In your case I think it may be something else. What's odd is when you push on the injector it pretty much goes away. If you have a JB4 I'd check for codes and then if none are found run a couple logs. Another alternative would be to have a well versed mechanic you trust try and diagnose it. Good luck.

Given your host of previous problems, your car sounds like a mess. "Touching" random parts to see if the noise goes away is pointless. You need to take it into a fresh *qualified* shop, that hasn't touched it before, so that they can properly diagnose your current issue(s).

[JuniorMint335]

Originally Posted by jtswole

Question. Why did you replace the rod bearings? If it's because of a spun bearing, you can't just replace the bearing and away you go. You need to replace the rod that spun the bearing, as well. The rod bearing will fail again and that is what you might hear.

Yeah I had a spun rod bearing. I got a new set of rods and bearings.

[JuniorMint335]

Any chance that the coil latch gets loose overtime? I see ECS tuning selling individual latches. Just a thought.

Feels like something is loose, weather its the coil not tight enough or the latch not holding on to the connector tight enough. I'll try it with a diff coil tonight.

[///mfizzle]

check your spark plug torque specs, should be 23nm.

or heck, just see if they're tight.

Sounds stupid, but it was a very common problem for e36 plugs to become loose an sound EXACTLY like your car. I've seen it happen a couple times at the dealership, including once on my personal e36 m3.

You pushing on the coil could be smashing the plug tighter

[///mfizzle]

worth a shot

[JuniorMint335]

Originally Posted by ///mfizzle

check your spark plug torque specs, should be 23nm.

or heck, just see if they're tight.

Sounds stupid, but it was a very common problem for e36 plugs to become loose an sound EXACTLY like your car. I've seen it happen a couple times at the dealership, including once on my personal e36 m3.

You pushing on the coil could be smashing the plug tighter

Wow sounds exactly like it. I wish I found this video earlier. Thanks for uploading the video.

I JUST CAME BACK FROM THE GARAGE AND HAPPY TO ANNOUNCE THAT IT IS INDEED THE STUPID PLUGS. Just out of curiosity, I took all the plugs out (1,2,3,4 knocks). I compare those plugs to 5,6. I noticed 1,2,3,4 all have spun plugs. I can literally spin the white part of the plug, but somehow it still manages to stay intact with the bottom. While 5 and 6 are not spun. This explains why when I press the coils, it quiets down.

FUKINGGG A. I shoulda took all the plugs out earlier and not just focusing on the knocking ones.. Question is HOW THE HELL CAN A PLUG GET SPUN??? HEAT?? WHAT CONNECTS THEM TOGETHER WITH THE BOTTOM, DOESNT SEEM MECHANICAL. HIGH TEMP GLUE? LOL

[WedgePerformance]

This engine is notorious for plugs coming loose. I've seen it on my cars multiple times.

[N54Society]

Yay, problem solved. Glad it wasn't a spun rod like some were suggesting. Always start with the easy stuff when it comes to troubleshooting.

[NapsterAU]

Originally Posted by JuniorMint335

Wow sounds exactly like it. I wish I found this video earlier. Thanks for uploading the video.

I JUST CAME BACK FROM THE GARAGE AND HAPPY TO ANNOUNCE THAT IT IS INDEED THE STUPID PLUGS. Just out of curiosity, I took all the plugs out (1,2,3,4 knocks). I compare those plugs to 5,6. I noticed 1,2,3,4 all have spun plugs. I can literally spin the white part of the plug, but somehow it still manages to stay intact with the bottom. While 5 and 6 are not spun. This explains why when I press the coils, it quiets down.

FUKINGGG A. I shoulda took all the plugs out earlier and not just focusing on the knocking ones.. Question is HOW THE HELL CAN A PLUG GET SPUN??? HEAT?? WHAT CONNECTS THEM TOGETHER WITH THE BOTTOM, DOESNT SEEM MECHANICAL. HIGH TEMP GLUE? LOL

I did suggest checking plugs but glad you got it figured out.
Best to just buy some new plugs to avoid issues down the road.